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Diarrhea is a significant cause of morbidity
and mortality in the neonatal foal. Numerous noninfectious
and infectious agents are responsible for enterocolitis and
enteritis. This article provides an overview of the
differential diagnoses for neonatal diarrhea and general
and specific guidelines for therapy.
Many causes of diarrhoea result in abdominal pain before
abnormal faeces are observed. Contagious causes of faol
diarrhoea are spread by environmental-oral or faecal-oral
transmission. In the equine neonate enteritis/diarrhoe is
one of the signs of sepsis. The diagnosis can be difficult
because the diagnostic methods have limitations. There are
often important herd considerations as well as individual
factors. Frequently, a potential pathogen is not
identified. Radiography and ultrasonography are important
diagnostic aids for evaluating foals with abdominal
Diarrhoea can cause dehydration and significant acid-base
and electrolyte imbalances in a very short period of time,
especially in young foals. Early diagnosis and carefully
considered treatment are important.
Causes, diagnosis, therapy and prevention of foal
• Foal heat diarrhoea.
This occurs most frequently at the time that corresponds
with dam’s first postpartum oestrus, and is probably
related to the natural faunation that occurs in foals
between 1 and 2 weeks of age. It is most likely caused by
hypersecretion in the small intestinal mucosa, which may
overwhelm an immature colon that is unable to compensate by
increased fluid and electrolyte absorption.Usually no
therapy is required. After cleaning the foal’s perineum, a
water repellent ointment can be used to prevent scalding
and hair loss.
• Nutrional causes
(overfeeding, sudden diet changes, foreign material).
Overfeeding, failure to adhere to instructions for milk
replacers and sudden diet changes of the mare and/or foal
should be avoided. Eating foreign material (sand, etc.)
should be prevented as this also may cause irritation of
the gastrointestinal tract.
• Lactose intolerance.
Primary lactose-intolerance from a congenital deficit or
absence of lactase in the brush border of the small
intestine is rare in foals but secondary lactose
intolerance may occur after many small intestine infections
as a result of the loss of lactase-producing intestinal
cells. Supplementation with lactase (fresh yoghurt) may
have a benificial effect.
• Viral intestinal
disease (Rotavirus, Coronavirus). Rota-virus
infection is probably the most common infectious cause of
faol diarrhoea. The severity of the disease is determined
by immune status, inoculation dose and the age of the foal.
Adult carriers and infected foals may shed rotavirus, and
the organisms may persist in the environment for up to 9
months. After oral infection the virus replicates the
villous tips of the small intestine, and these cells are
destroyed. The gut looses absorptive function and probably
alos the ability to produce lactase. Fals may be anorectic,
depressed and develop diarrhoea within 24h. Fever is not
always present. Diagnosis can be made with a test on
faeces. Foals should be kept on mare’s milk, intravenous
rehydration and electrolyte balancing may be needed.
• Helminth parasites. Strongyloides westeri may affect as
may as 90% of young foals, but is usually non-symptomatic
except when present in enormous numbers. Foals can acquire
a patent infection as early as 8-12 days of age because
transmission of larvae is transmammary or incidentally
through penetration of the skin. Prevention is achieved
through deworming the mare with ivermectin 1-2 weeks before
the expected parturition date. Incidentally, haevy
infection with Strongyle spp. may cause diarrhoea in older
foals. Diagnosis may be difficult as faecal samples will be
negative for eggs. Parascaris equorum is more commonly
associated with intestinal obstructiopn than diarrhoea.
• Protozoan parasites
(Cryptosporidium). The role of Cryptosporidium spp. in foal
diarrhoea is controversial. Clinical infection in
immunocompetent animals is slef-limiting, but fatal
enterocolitis and chronic diarrhoea have been reported.
Diagnosis is made by detecting oocysts in a faecal sample.
Treatment is generally supportive.
• Anaerobic and aerobic
bacterial pathogens (Clostridium, E. Coli,
Salmonella, Rhodococcus equi). Clodstridium is an important
cause of enteric disease in young foals as it may produce
potent exotoxins that damage the mucosa and cause fluid
loss into the gut lumen and peritonal cavity. Affected
foals can develop severe colic with gas distension
preceding the (haemorrhagic) diarrhoea or they may die
acutely of shock. Treatment is often disappointing but
should consist of fluid therapy and antimicrobial agents.
Clostridium is often associated with stress,
antibiotic-associated diarrhoea and hospital environments,
and clinical signs range from mild diarrhoea to severe
necrotising haemorrhagic enterocolitis.
E. Coli has rarely been associated with diarrhoea in foals,
although it is the most common cause of septicaemie in
In foals, infection with Salmonella spp. mostly occurs as
isolated cases. The mare appears to be the primary source
of infection in most cases. Affected foals usually have
moderate to severe clinical signs that include fever,
diarrhoea, dehydration, profound depression and reduced
appetite. The diagnosis is confirmed by faecul culture.
Rhodococcus equi usually causes respiratory problems, but
occasionally infected foals may have acute or, more often,
• Gastric ulceration
• Antibiotic associated